Suppressing bias stress degradation in high performance solution processed organic transistors operating in air

Hamna F Iqbal,Oana D Jurchescu,Karl J Thorley,Chad Risko,Qianxiang Ai,Hu Chen,John E Anthony,Iain Mcculloch

doi:10.1038/s41467-021-22683-2

Abstract

Solution processed organic field effect transistors can become ubiquitous in flexible optoelectronics. While progress in material and device design has been astonishing, low environmental and operational stabilities remain longstanding problems obstructing their immediate deployment in real world applications. Here, we introduce a strategy to identify the most probable and severe degradation pathways in organic transistors and then implement a method to eliminate the main sources of instabilities. Real time monitoring of the energetic distribution and transformation of electronic trap states during device operation, in conjunction with simulations, revealed the nature of traps responsible for performance degradation. With this information, we designed the most efficient encapsulation strategy for each device type, which resulted in fabrication of high performance, environmentally and operationally stable small molecule and polymeric transistors with consistent mobility and unparalleled threshold voltage shifts as low as 0.1 V under the application of high bias stress in air.

Highlights

Solution processed organic field effect transistors can become ubiquitous in flexible optoelectronics
We delivered robust Organic field-effect transistors (OFETs) with unparalleled operational stability regardless of the composition and configuration, as confirmed by the constant mobility and exceptionally low threshold voltage shift of ΔVth = 0.1 eV achieved under aggressive bias stress conditions for 500 min in ambient air
Operational stability tests were first performed on bottom-contact, bottom-gate OFETs with the semiconducting layer consisting of the small molecule tri(n-hexyl)silylethynyl benzodithiophene (TnHS BDT) trimer and SiO2 gate dielectric (Fig. 1)[34]

Summary

Introduction

Solution processed organic field effect transistors can become ubiquitous in flexible optoelectronics. Real time monitoring of the energetic distribution and transformation of electronic trap states during device operation, in conjunction with simulations, revealed the nature of traps responsible for performance degradation With this information, we designed the most efficient encapsulation strategy for each device type, which resulted in fabrication of high performance, environmentally and operationally stable small molecule and polymeric transistors with consistent mobility and unparalleled threshold voltage shifts as low as 0.1 V under the application of high bias stress in air. By monitoring the energetic distribution and time evolution of trap states during OFET operation, and with guidance from density functional theory (DFT) calculations, we gained access to the origins of device degradation, clarified the nature of the traps generated during operation, and the parameter space that gives rise to these traps This information guided the development of efficient encapsulation pathways that offer selective transparency to some species while blocking the species responsible for degradation.

Methods

Results

Conclusion